Before Ma-tsu became a teacher, he was training at Nan-yueh’s monastery, one of several hundred monks lost in the crowd.  A senior monk noticed how diligent he was and mentioned him to Nan-yueh, who found him alone in the zendo and asked, ‘What is your purpose in doing zazen?’  When Ma-tsu replied, “I seek to become a Buddha’, Nan-yueh picked up a tile and began rubbing it with a stone.  Ma-tsu was surprised.  “What are you doing?” The teacher said, “I’m polishing this tile to make a mirror.”  Ma-tsu asked, ‘Can a piece of roofing tile be made into a mirror?’  Nan-yueh asked in return, “Can a Buddha be created by doing zazen?”  Their dialogue continues,  Nan-yueh encouraging Ma-tsu, who realises the mind-ground. What is your purpose?

This teisho (case 30 of the Mumonkan) was given by Gillian Coote, roshi on day 3 of Spring sesshin 2025 at Kodoji.